title: RKIP phosphorylation and STAT3 activation is inhibited by oxaliplatin and camptothecin and are associated with poor prognosis in stage II colon cancer patients.
abstract: BACKGROUND
  A major obstacle in treating colorectal cancer (CRC) is the acquired resistance to chemotherapeutic agents. An important protein in the regulation of cancer cell death and clinical outcome is Raf kinase inhibitor protein (RKIP). In contrast, activated signal transducer and activator of transcription 3 (STAT3) is a protein that promotes tumor cell survival by inhibiting apoptosis and has an important role in cancer progression in many of cancer types. The aim of this study was to evaluate the regulation of RKIP and STAT3 after treatment with clinically relevant chemotherapeutic agents (camptothecin (CPT) and oxaliplatin (OXP)) and the cytokine interleukin-6 (IL-6) in HCT116 colon cancer cells as well as evaluate the association between RKIP and STAT3 with clinical outcome of Stage II colon cancer patients.
  
  
  METHODS
  HCT-116 colon cancer cells were treated with CPT, OXP, and IL-6 separately or in combination in a time and dose-dependent manner and examined for phosphorylated and non-phosphorylated RKIP and STAT3 via Western blot analysis. STAT3 transcriptional activity was measured via a luciferase reporter assay in HCT116 cells treated with CPT, IL-6 or transfected with JAK 1, 2 separately or in combination. We extended these observations and determined STAT3 and RKIP/ pRKIP in tumor microarrays (TMA) in stage II colon cancer patients.
  
  
  RESULTS
  We demonstrate IL-6-mediated activation of STAT3 occurs in conjunction with the phosphorylation of RKIP in vitro in human colon cancer cells. OXP and CPT block IL-6 mediated STAT3 activation and RKIP phosphorylation via the inhibition of the interaction of STAT3 with gp130. We determined that STAT3 and nuclear pRKIP are significantly associated with poor patient prognosis in stage II colon cancer patients.
  
  
  CONCLUSIONS
  In the analysis of tumor samples from stage II colon cancer patients and the human colon carcinoma cell line HCT116, pRKIP and STAT3, 2 proteins potentially involved in the resistance to conventional treatments were detected. The phosphorylation of pRKIP and STAT3 are induced by the cytokine IL-6 and suppressed by the chemotherapeutic drugs CPT and OXP. Therefore, these results suggest that STAT3 and pRKIP may serve as prognostic biomarkers in stage II colon cancer patients and may improve chemotherapy.
authors.affiliation: Department of Medicine, Rhode Island Hospital and The Alpert Medical School of Brown University, Providence, RI 02903, USA. Devasis_Chatterjee@Brown.edu.
authors.forename: Sam
authors.initials: S
authors.lastname: Cross-Knorr
authors.forename: Shaolei
authors.initials: S
authors.lastname: Lu
authors.forename: Kimberly
authors.initials: K
authors.lastname: Perez
authors.forename: Sara
authors.initials: S
authors.lastname: Guevara
authors.forename: Kate
authors.initials: K
authors.lastname: Brilliant
authors.forename: Claudio
authors.initials: C
authors.lastname: Pisano
authors.forename: Peter J
authors.initials: PJ
authors.lastname: Quesenberry
authors.forename: Murray B
authors.initials: MB
authors.lastname: Resnick
authors.forename: Devasis
authors.initials: D
authors.lastname: Chatterjee
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000970:Antineoplastic Agents / Q000494:pharmacology*; D002166:Camptothecin / Q000494:pharmacology*; D003110:Colonic Neoplasms / Q000235:genetics / Q000378:metabolism* / Q000401:mortality* / Q000473:pathology; D050822:Cytokine Receptor gp130 / Q000378:metabolism; D005260:Female; D015870:Gene Expression; D006801:Humans; D015850:Interleukin-6 / Q000378:metabolism / Q000494:pharmacology; D053612:Janus Kinases / Q000378:metabolism; D008297:Male; D008875:Middle Aged; D060787:Neoplasm Grading; D009367:Neoplasm Staging; D009944:Organoplatinum Compounds / Q000494:pharmacology*; D000077150:Oxaliplatin; D049488:Phosphatidylethanolamine Binding Protein / Q000378:metabolism*; D010766:Phosphorylation / Q000187:drug effects; D011379:Prognosis; D011485:Protein Binding; D050796:STAT3 Transcription Factor / Q000037:antagonists & inhibitors* / Q000235:genetics / Q000378:metabolism; D015398:Signal Transduction / Q000187:drug effects; D014158:Transcription, Genetic; D047368:Tumor Burden
chemical_list: D000970:Antineoplastic Agents; D015850:Interleukin-6; D009944:Organoplatinum Compounds; C511482:PEBP1 protein, human; D049488:Phosphatidylethanolamine Binding Protein; D050796:STAT3 Transcription Factor; D000077150:Oxaliplatin; D050822:Cytokine Receptor gp130; D053612:Janus Kinases; D002166:Camptothecin